System Design for Geosynchronous Synthetic Aperture Radar Missions

Geosynchronous Synthetic Aperture Radar (GEO SAR) is a possible next generation SAR system, which has the excellent performance of less than one-day revisit and hundreds of kilometres coverage. However, Radio Frequency Interference (RFI) is a serious problem, because the specified primary allocation frequencies are shared by the increasing number of microwave devices. More seriously, as the high orbit of GEO SAR makes the system have a very large imaging swath, the RFI signals all over the illuminated continent will interfere and deteriorate the GEO SAR signal. Aimed at the RFI impact in GEO SAR case, this paper focuses on the performance evaluation and the system design requirement of GEO SAR in the presence of RFI impact. Under the RFI impact, Signal-to-Interference-plus-Noise Ratio (SINR) and the required power are theoretically deduced both for the ground RFI and the bistatic scattering RFI cases. Based on the theoretical analysis, performance evaluations of the GEO SAR design examples in the presence of RFI are conducted. The results show that higher RFI intensity and lower working frequency will make the GEO SAR have a higher power requirement for compensating the RFI impact. Moreover, specular RFI bistatic scattering will give rise to the extremely serious impact on GEO SAR, which needs incredible power requirements for compensations. At last, real RFI signal behaviours and statistical analyses based on the SMOS satellite, Beidou-2 navigation satellite and Sentinel-1 A data have been given in the appendix.

Section: Bandmentioning

confidence: 99%

Performance and Requirements of GEO SAR Systems in the Presence of Radio Frequency Interferences

Guarnieri

et al. 2018

“…Even in the area with a lower fringe frequency, the largest deformation retrieval error in the scene is higher than 0.2 m and the mean square root error of the deformation is 0.13 m, which cannot satisfy the requirements for the deformation retrieval accuracy in any engineering applications. Therefore, some compensation algorithms based on Persistent Scatterer technology (PS) [4,[33][34][35][36][37] or some similar methods based on the high quality coherent points are really needed to eliminate the serious impacts of the interferometric phase screen errors brought by the temporal-spatial background ionosphere variation in GEO D-InSAR processing in the future. Utilizing the USTEC data in Figure 4 and Equation (14), the interferometric phase screen errors generated by 1 ( ) Φ P  and 2 ( ) Φ P  are shown in Figure 7a.…”

Section: Interferometric Phase Screen Errormentioning

confidence: 99%

“…It has a short revisit time of less than 24 h and extensive imaging coverage of more than 1000 km [4,5], which helps to realize the fast revisit and imaging of scenes of interest [6,7]. Therefore, the combination of GEO SAR and differential SAR interferometry (D-InSAR) can realize timely surface deformation detection, which has great advantages in the evaluation and forecast of natural disasters (earthquakes, landslides, volcano eruptions, etc.)…”

Section: Introductionmentioning

confidence: 99%

Impacts of Temporal-Spatial Variant Background Ionosphere on Repeat-Track GEO D-InSAR System

Dong

et al. 2016

An L band geosynchronous synthetic aperture radar (GEO SAR) differential interferometry system (D-InSAR) will be obviously impacted by the background ionosphere, which will give rise to relative image shifts and decorrelations of the SAR interferometry (InSAR) pair, and induce the interferometric phase screen errors in interferograms. However, the background ionosphere varies within the long integration time (hundreds to thousands of seconds) and the extensive imaging scene (1000 km levels) of GEO SAR. As a result, the conventional temporal-spatial invariant background ionosphere model (i.e., frozen model) used in Low Earth Orbit (LEO) SAR is no longer valid. To address the issue, we firstly construct a temporal-spatial background ionosphere variation model, and then theoretically analyze its impacts, including relative image shifts and the decorrelation of the GEO InSAR pair, and the interferometric phase screen errors, on the repeat-track GEO D-InSAR processing. The related impacts highly depend on the background ionosphere parameters (constant total electron content (TEC) component, and the temporal first-order and the temporal second-order derivatives of TEC with respect to the azimuth time), signal bandwidth, and integration time. Finally, the background ionosphere data at Isla Guadalupe Island (29.02 • N, 118.27 • W) on 7-8 October 2013 is employed for validating the aforementioned analysis. Under the selected background ionosphere dataset, the temporal-spatial background ionosphere variation can give rise to a relative azimuth shift of dozens of meters at most, and even the complete decorrelation in the InSAR pair. Moreover, the produced interferometric phase screen error corresponds to a deformation measurement error of more than 0.2 m at most, even in a not severely impacted area.

“…[4], so it has significant application potential for disaster prevention and mitigation, including flood disaster, geological disaster, etc. [1,[5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Formation Design for Single-Pass GEO InSAR Considering Earth Rotation Based on Coordinate Rotational Transformation

Chen

Dong

et al. 2020

The single-pass geosynchronous synthetic aperture radar interferometry (GEO InSAR) adopts the formation of a slave satellite accompanying the master satellite, which can reduce the temporal decorrelation caused by atmospheric disturbance and observation time gap between repeated tracks. Current formation design methods for spaceborne SAR are based on the Relative Motion Equation (RME) in the Earth-Centered-Inertial (ECI) coordinate system (referred to as ECI-RME). Since the Earth rotation is not taken into account, the methods will lead to a significant error for the baseline calculation while applied to formation design for GEO InSAR. In this paper, a formation design method for single-pass GEO InSAR based on Coordinate Rotational Transformation (CRT) is proposed. Through CRT, the RME in Earth-Centered-Earth-Fixed (ECEF) coordinate system (referred to as ECEF-RME) is derived. The ECEF-RME can be used to describe the accurate baseline of close-flying satellites for different orbital altitudes, but not limited to geosynchronous orbit. Aiming at the problem that ECEF-RME does not have a regular geometry as ECI-RME does, a numerical formation design method based on the minimum baseline error criterion is proposed. Then, an analytical formation design method is proposed for GEO InSAR, based on the Minimum Along-track Baseline Criterion (MABC) subject to a fixed root mean square of the perpendicular baseline. Simulation results verify the validity of the ECEF-RME and the analytical formation design method. The simulation results also show that the proposed method can help alleviate the atmospheric phase impacts and improve the retrieval accuracy of the digital elevation model (DEM) compared with the ECI-RME-based approach.The performance of InSAR and TomoSAR based on monostatic GEO SAR significantly degrades due to temporal decorrelation (caused by the scene scattering fluctuation during the observation time gap between repeated tracks) and atmospheric disturbance. Similar to LEO SAR [8], we can use the formation GEO SAR to form a real-time baseline to improve interferometry performance [9,10], realizing single-pass GEO InSAR. Additionally, multiple phase centers can be generated in GEO SAR formation, and a flexible baseline configuration can enrich the functions.The primary task of SAR formation is to design the satellite orbital elements to obtain a reasonable formation configuration and then meet the application performance requirements. The formation design of LEO SAR has been adequately studied, and a very mature solution has been found. A very typical method is to describe the geometry of the formation using the Relative Motion Equation (RME) based on the difference between the master satellite's and slave satellite's orbital elements, and combining the mission requirements to design the satellite's orbital elements [11].The theoretical study of the Relative Motion Equation has gone through three stages. The earliest form of RME, which was used to complete spacecraft rendezvous and docking tasks [12], was obtain...